1. Field of the Invention
The present invention relates to a method of inspecting a body having through holes, in which a fine-gap (or narrow-gap) groove is formed in at least a part of each through hole, and relates to a method of repairing the body, specifically, repairing an abnormal part in a defective through hole. The method is applicable for inspecting and repairing various types of a body such as a honeycomb structure molding die for use of producing honeycomb structure bodies having fine-gap slit grooves.
2. Description of the Related Art
There is a molding die such as an extrusion die as an example of various types of a body having fine-gap (or narrow-gap) grooves. A monolith honeycomb type structure body (hereinafter, referred to as the “honeycomb structure body” for short) is extruded through such a molding die. The honeycomb structure body acts as a catalyst carrier of a catalytic converter for motor vehicles. The catalytic converter is mounted on an exhaust gas pipe in a motor vehicle. Through the exhaust gas pipe, the exhaust gas emitted from an internal combustion engine is flowing and purified by the catalytic converter. Such a honeycomb structure body is extruded using the molding die.
Recently, in order to improve the exhaust gas purifying function of the honeycomb structure body as an exhaust gas purifying converter and further to certainly perform the exhaust gas purifying function of the honeycomb structure body immediately after an internal combustion engine start of the motor vehicle starts, the thickness of cell walls formed in the honeycomb structure body is decreases as thin as possible. Accordingly in order to achieve the recent demand described above, the gap or interval between the adjacent slit grooves in the molding die, through which the ceramic material is extruded, is more decreased.
For example, Japanese patent NO. JP3750348 as a related art technique has disclosed the method of producing such a molding die. Through the molding die, a honeycomb structure body is extruded or produced. In the related art technique disclosed in Japanese patent NO. JP3750348, slit grooves are formed in a metal material using a thin blade grindstone as a cutting tool. Fine powder of metal generated by cutting the metal material during the slit groove formation is removed by sucking it through feed holes in order to remove fine powder of metal from the slit grooves and the feed holes in the molding die.
Because each slit groove disclosed in Japanese patent NO. JP3750348 is within a range of 105 to 110 μm, it is possible to remove the fine powder of metal by sucking from the metal material as a working material. However, as described above, because the thickness of the cell wall in the honeycomb structure body is more decreased as thin as possible, the recent demand needs having each slit groove in the molding die of a width of approximate 75 μm in a narrow dimension. It is however difficult to completely remove the remaining fine metal of powder remained in the slit grooves and the feed holes in the molding die by sucking. As a result, the fine power of metal is still remained in the slit grooves of the molding die even if sucking is carried out during the slit groove formation. Furthermore, this causes a possibility of deform the surface of the slit grooves and feed holes through which molding material is fed and extruded in addition to choking the slit grooves with the fine powder of metal during the manufacture of the molding die. That is, the related art techniques cause the deformation in through holes (or penetrated holes) composed of fine-gap grooves (or slit grooves) and the feed holes in the molding die. It is further difficult to detect the presence of defects, namely, abnormal parts such as a deformation part and a remaining foreign matter in the slit grooves of the molding die immediately after the molding die is produced.
In the present time, the related art techniques can detect or find the presence of defects such as an abnormal part (a deformation part and fine powder of metal generated by cutting a metal material) in the molding die by inspecting a honeycomb structure body produced or extruded using the molding die in an experimental test for the molding die. In other words, the related art technique can not find the abnormal part in the molding die by directly inspecting the molding die. That is, the related art techniques detect or find the presence of defect such as a deformation part and a remaining foreign matter (remaining fine powder of metal) in the molding die using the honeycomb structure body which is produced using the molding die. Accordingly, the related art techniques must produce or extrude the honeycomb structure body in order to inspect the molding die. The molding die is then repaired or replaced with a new molding die if the presence of defect is discovered after inspecting the honeycomb structure body produced using the molding die. This causes the loss of time and production material resources in manufacture, and increasing the work in the series of production of the molding die and the honeycomb structure body.